Radar antenna stabilizer



Jufiy 12, 1949. T. w. KENYON RADAR ANTENNA STABILIZER 5 Sheets-Sheet 1Filed Jan. 25, 1947 JNVENTOR. M/ Kz/vm/v *W A 7 TUE/VLYS Wyn/4 7 Jufly12, 194%. Tfw. KENYON RADAR ANTENNA STABILIZER 5 Sheets-Sheet 2 FiledJan. 25, 1947 5 v, W mm We V5 0 WK K W 5. W 2 w July 112, 1949. T. w:KENYON 294759746 RADAR ANTENNA STABILIZER Fi led Jan. 25, 1947 5Sheets-Sheet 5 July 12, 1949. T. w. KENYON RADAR ANTENNA STABILIZERFiled Jan. 25, 1947 5 Sheets-Sheet 4 v F INVENTOR. 79.50%25 W KA Wow W4770/Z/ f 5 July 12, 1949. T. w. KENYON RADAR ANTENNA STABILIZER FiledJan. 25, 1947 5 Sheets-Sheet 5 INVENTOR. $95900 W Km mn/ Patented July12, 1949 UNITED STAS RADAR ANTENNA STABILIZER Application January 25,1947, Serial No. 724,342

3 Claims.

This invention relates to a stabilizer for a radar antenna and moreparticularly to a stabilizer arrangement for such antenna to be used inconjunction therewith when the antenna is mounted in or upon anaircraft.

It is essential to stabilize the antenna of an airborne radar so thatthe picture presented to the observer in the airplane will not shift,tilt or leave the field of view while the airplane is either banked withchanges in its transverse axis direction, or while its pitch orlongitudinal axis changes direction or while a combination of these twomotions occurs. Such changes in the airplane axes may either beaccidental as, for example, the result of an air bump or directly theresult of a turn or climb or a combination of the latter two.

The antenna consists of a reflector that is usually parabolic and asuitable radiator together with associated equipment which are rotatedor oscillated about a vertical axis at various speeds in theneighborhood of 60 revolutions per minute. The necessary driving andcontrol motors, the bearings, the radar guide power joints andassociated equipment generally comprise a fairly heavy assembly.Heretofore, some attempts have been made to stabilize the whole assemblyin order to compensate for changes in the airplane attitude. While thisapproach is feasible, it is cumbersom'e, slow acting, and requirespowerful servo-motors which are large and require considerable energy tooperate them. Moreover, the inertia of the large masses makes itdifficult to secure quick and accurate stabilization.

A principal object of this invention is to provide a simple stabilizingarrangement in which it is possible to secure desired uniformlymaintained directional effect of a radar antenna on an aircraft bycompensating adjustment simply of the radar reflector without requiringadjustment or stabilization of the entire support and mechani-' calequipment associated with the antenna.

Another object of the invention is to provide a simple mechanical systemfor efiecting the desired stabilization which is responsive quickly andaccurately to changes resulting from changes in pitch or bank of theaircraft or a combination of these two.

A further object of the invention is to provide apparatus of thecharacter described that is operated simply by light low poweredservo-motors controlled in turn, for example, by a gyroscope.

Another object of the invention is to provide a stabilizing arrangementwhich eliminates the necessity for effecting stabilization of the entireradar antenna and its complicated heavy associated mechanisms.

A further object of the invention is to provide a stabilizingarrangement that is mechanically sound, has a minimum of operating partsand that is comparatively simple and easy to construct and assemble.

Yet another object is to provide a stabilizing arrangement whichobviates the necessity for stabilizing heavy massive equipmentassociated with the radar antenna.

To the accomplishment of the foregoing and such other objects as mayhereinafter appear, the invention comprises the novel construction andarrangement of parts hereinafter to be described and then sought to bedefined in the appended claims, reference being had to the accompanyingdrawings forming a part hereof, which show merely for the purposes ofillustrative disclosure, a preferred embodiment of the invention, itbeing expressly understood, however, that changes may be made inpractice within the scope of the claims without digressing from theinventive idea.

In the drawings in which similar reference characters denotecorresponding parts:

Fig. 1 is a front elevation of a proposed embodiment of the mechanism inwhich the radar reflector is the part receiving compensating adjustmentto compensate for changes in roll (bank) or pitch of the aircraft;

Fig. 2 is a side elevation of the device of Fig. 1;

Fig. 3 is a similar side elevation of the opposite side of the device ofFig. 1;

Fig. 4 is a rear elevation of the device of Fig. 1;

Fig. 5 is a transverse section taken along 5-5 of Fig. 2 and viewed inthe direction of the arrows;

Fig. 6 is a vertical section taken along line 6-6 of Fig. 4 and viewedin the direction of the arrows;

Fig. 7 is a transverse section taken along line l-1 of Fig. 6 and alsoviewed in the direction of the arrows;

Fig. 8 is a side elevation similar to that of Fig. 2 illustrating theposition assumed by the parts when the aircraft is in a bankingposition;

Fig. 9 is a similar view with the entire antenna rotated about thesupport axis from the position shown in Fig. 8;

Fig. 10 is a side elevation similar to that of Fig. 3 showing theposition assumed by the parts when the aircraft has both roll or bankand pitch; and

Fig. 11 is a view similar to'that of Fig. 10 when the antenna assemblyhas been rotated about its support axis to a different position fromthat of Fig. 10. v

Referring to the drawing, l denotes some portion of the aircraft, forexample, one of the crossbars of the fuselage frame or any other rigidportion of the craft. The radar antenna com-- prises a reflector llusually parabolic and a radiator l2 which is positioned to extendforwardly of the reflector ll along the focal axis FF thereof. A bracketI3 which, in the embodiment shown, is substantially U-shaped, is securedto the rear of the reflector II. This bracket I3 is secured pivotally atM to a stub shaft Hi. This shaft 15 has an extension iii-ofreduceddiameter which is rotatably borne in a bearing I! (Fig. 6). Thebearing-I!' is fixedly supported between the uppenportions of a pair of rigidframe members I8; 1'9 (Fig. 3)" so that the normal position of shaft l5,lfiishorizontal. Each of the frame members [8, l'9 extends downwardlyfrom the bearing l1 and the lower ends of'the'se frame members arejoined to opposite faces of a blockZll. The block 20 in turn has a.shaft part 2| (Fig. 6) of reduced diameter that is borne normallyvertically-ina bearing--22 carried by the airplane frame part II]. Anextension 23 of the shaft part 2| of smaller diameter than the latterextends through an opening in the frame part If! and has a gear 24splined or otherwise fixed thereto for rotating the shafts 23, 21, theblock part 20 and the two-frame parts l8, [9 about thenormally verticalaxis'of theshaft parts 2i and 23. The latter axis constitutes thesupport axis of the antenna. The'normal and'fixed disposition of theshaft l'5and its-extension l3 in the bearing IT is at right angles tothe support axis of the shafts 2|- and 23. Forpurposes presently to bedescribed, the shaft po'rtionsl5. l3 and the block 28 and its associatedshaft parts '2 I, 23- are hollow. For convenience the block 20, framemembers 1-8, I Sand block ll'ma'y be designated as the antenna mast ormast assembly.

The angle of tiltof the reflector l-l' relative to the pivot l4 and,consequently; with respect to the mast is adjustable, means, however,being provided for maintainingany adjusted tilt position. For thispurpose bracket arm members 25= are secured suitably to extend from theback face of the reflector H. A cam 26 issupported'on an adjustableshaft 21' carried by the bracket members 25. The shaft 2! in turn-isconnected by conventional flexible drive cable 28 toa tilt motor 29carried conveniently onthe bearing block 11. This tilt motoris'conne'cted electrically or mechanically to controlls provide'dyforexample. in the cockpit of. the plane-andin' usual practice has anoperating range of' approximately'l5" so that desired adjustment of thecam'2B'may-be' effected from the cockpit, with corresponding changes inthe tilt-of the reflector l'l about its pivot ML. To this end, the camfollower rlod.3'0'operates on the surface of the cam 26. This followerrod 3!! is supported suitably between a pair of arms 3| which in turn,are attached fixedly to. the opposite legs of the, U-shaped-bracket l3.The cam follower rod 3!! is in.the,f0rm off a cross-bar. extendingbetween. the arms 3]. U-shaped crosspiece 32 is. carried rotatably onthe cam follower. rod. 30 and extends rearwardlv of the latter for engaement with a cross-head. The cross-head 33is attached to the ends of apair of'sliderod's 34, '35"w'hich are borne slidably in appropriateguideways 3B, 31' provided in the bearing block 11.

The opposite ends of'th'exslide rods 34, 35 are joined by a cross-bar38. The'cross-bar, 38. is in turn adapted to be engaged by a camfollower A substanti'ally- 39 provided on a crank 40. The crank 40 issplined or otherwise fixed to a rotatable shaft 4| extending between andcarried suitably by the frame members i8 and I9. A second crank 42likewise is fixed or splined to the shaft 4!. The crank 42 is pivotallysecured at 43 to the linkage 44. This linkage 44 in turn is securedpivotally at 45 to a crank 46 (Fig. 8). A second crank 41 is secured infixed angular relationship to the crank 43 and the two cranks 46 and 41are secured pivotally at 48 to the frame part 19. The crank 41 has alaterally extending portion 41a. A cam follower in the form of a roller49 is rotatably carried on a'stub shaft 50 which is secured to thelaterally extending portion 410. of the crank 41 for purposes presentlyto be described. The axis of the stubshaft 50 carrying roller 49 liessubstantially at right angles to the axis of the pivot 48. As the cranks46, 4'! are rotated about the pivot 48, the link 44 coupled to crank 46effects rotation of cranks 4-2 and 40: Such movement of the crank 40isimparted as sliding motion to the slide rods 34,35; inthe block H. Thesliding motion of rods 34, 35 in turn through the engagement of crossbar33, and crosspiece 32 operates when moved toward the reflector l l torotate the arms 3| and thusto rotate thereflector about its pivotal axisit, i. e., to tilt the reflector. Suitable biasing means presently to bedescribed are provided to maintain the engagement between the crosspiece32 and cross-bar 33.

A crank 51 is secured fixedly or splined to the reduced portion l6 ofthe stub shaft l5 which extends rearwar-dly of bearing l1. This crankis. connected pivotally'at 52 to the link 53 (Figs.

10 and 11), the latter is connected at 54 to a linkage 55. The portion55a of the linkage 55 is connected pivotally at 56' to a substantiallyU-shaped yolk 51. The yolk 51 is secured pivotally at 58and 59 toopposite faces of the block A cam follower roller 60 is rotatablysupported on a stubshaft 6| carried by theyolk 5 1. The axis of thestubshaft 6| carrying roller 50: lies substantially at right angles tothe axis of the pivots 58, 59'. Rotation of the yolk 51 aboutits'pivots- 58, 59 is transmitted by the linkage"55-,-and link 53 tothe-crank 5|. This crank in turn correspondingly rotates the shaft l5,l6 about itslongitudinal axis for purposes presently to be described.The rollers 49 and 60 which respectively thus control pivotal or tiltmotion of reflector ll about its pivotal axis [4 and its angular shiftwith the shaft l5, [6 are controlled as will now be described.

An outer gimbal ring 62 is-supported by the diametrically oppositelylocated pivots 63, 64 (Fig. 5) which-in turn are supported fromtherespective uprights 65' and 66 secured, for example, to the frame partI0.- A second or inner gimbal ring 6'1 is supported-by the diametricallyoppositely located pivots 68- and 69. The latter pivots are spaced apartwith respect to thepivots63 and fi l-and are supported by the outergimbal ring 62. The second or inner gimbalring- 5! has an internalgroove'fi'la (Fig. 6) which serves as a trackway for the two rollers 49and 60, sufficient clearance being provided between the rollers and thegroove walls to permit the rollers to rotate. This clearance is of theorder of a few thousandths of an inch so that backlash is negligible.

A servo-motor 10 (Fig. 3) of conventional type either electrical orhydraulic requiring comparatively little powerv for its operation issecured to the frame'part l0 adjacent the outer gimbal ring 62. By wayof example, this servo-motor which is of a reversible type has athreaded shaft 7! that receives a traveling nut 72. This nut 12 iscoupled, for example, by a linkage is to an arm 14 fixed to the outergimbal ring 62, preferably in a position 90 away circumferentially fromthe outer gimbal ring pivots 63, 64, so that rotation of the servo-motorshaft H in either direction with corresponding longitudinal movement ofthe travelling nut 12 on shaft II will function to rotate the gimbalring 62 about its pivotal supports 63, 64 in the correspondingdirection.

A second servo-motor 15 (Figs. 4 and 5) is secured preferably to aradially extending portion 62a. provided on the outer gimbal ring 62adjacent, for example, the pivot 64. This servomotor [5 is of the sametype as the servo-motor 10. It is provided with a threaded shaft 16 onwhich a travelling nut fl is movable in either direction depending uponthe direction of rotation of the shaft It. The travelling nut Tl has anarm 38 coupled by a linkage E9 to an arm 86 which is secured to extendfrom the inner gimbal ring ii. The arm 8!! preferably is located 90circumferentially from the inner gimbal ring pivots 68, 69 so thatoperation of the servomotor 15 will function to rotate the inner gimbalring Bl in required direction about its pivots E8, 69 depending upon thedirection of rotation imparted to the shaft '56 of the servo-motor 15.

As shown, the servo-motor i5 is located on the outer gimbal rin 62. Thisarrangement is preferable from the point of View of simplicity but notesential, inasmuch as the servo-motor 15 could be mounted on the framepart IQ if suitable coupling arrangements were provided to give therequired motion to the inner gimbal ring 61, irrespective of theposition of outer gimbal ring 82.

The two servo-motors 'H! and 15 are controlled respectively by thepositions of the corresponding gimbal rings (not shown) of a gyroscope Gfllustrated diagrammatically in Fig. 5 and located at some convenientpoint in the aircraft and designed to operate for the establishment of afixed axis direction irrespective of bank or pitch of the plane. As thegimbal rings of this gyroscope G change position to maintain the fixedaxis adjustment just described, the servomotors Hi and 15 by electric orfluid connection lines L and M with controls (not shown) operated by thegyroscopes gimbal rings (not shown) are corespondingly actuated. so thatthe outermost and innermost gimbal rings 6'2 and 6'! are movedautomatically to corresponding positions. In consequence, the rollers 49and 50 which travel in the trackway 51a provided in the inner gimbalring 6! as shafts 2!, 23 are rotated about their support axis, impartcompensating movements to the linkages and cranks associated with eachto maintain the parabolic reflector I! in its initially adjustedposition, shown for example in Fig. 2, as substantially vertical withthe radiator l2 extending along a horizontal axis. This position of thereflector H is maintained while the shafts 2! and 23 are oscillated orrotated about the support axis of these shafts through the agency of thegear 24 and irrespective of changes in pitch or bank of the plane, andthe angular disposition of said support axis.

A spring biasing means 82 is secured to the stub shaft l5. An arm 82athereof engages the rear surface of the reflector II. The purpose ofthis biasing means is to maintain a bias that vertical.

tends to rotate the reflector about the pivot M to maintain contactbetween the surfaces of the crosspiece 32 and the cross-head 33 and,also, between the surface of the cross-bar 38 and the cam follower 39 onthe crank M3. The stub shaft and the shafts 2i and 23 as well as theblock 28 are hollow to permit the passage through them of necessaryelectrical connections and, also, the wave guide 83 which is of a knownflexible form.

In the operation of the construction described, the gyroscope G is set,for example, to provide an erect axial position irrespective of the bankor pitch of the airplane. The servo-motors l0 and F5 are electricallyconnected to operate in response to the action of the gyroscope gimbalrings in known manner so that any change of the airplane position duringflight resulting in movement of the gyroscope gimbal rings will causethe transmission of impulses through the lines L and M to actuate theproper one of the servo= motors in and i5 or both of them to produce thenecessary changes in positions of the gimbal rings 62 and 6'! of thedevice herein described. For example, Figs. 8 and 9 illustrate whatoccurs if the airplane executes a bank only resulting in acounterclockwise rotation of the airplane part ill to the angularposition shown in Figs. 8 and 9. In order to maintain the reflector l lin the position shown in these figures which is its initially adjustedposition, as shown in Figs. 1 and 2. wherein the longitudinal axis ofthe radiator l2 lies horizontal and the transverse axes AA, BB of thereflector ll lie in a plane that is perpendicular to the horizontal, anddespite the bank of the plane, it is necessary for the gimbal rings 52and it? to maintain their coplanar relationship relative to each other.At the same time, however, it becomes necessary for them to be rotatedabout the pivots 63 and 64 in the clockwise direction so that theirplane assumes the horizontal, irrespective of the fact that the plane ofthe airplane part IE) is at an angle with the horizontal and the axis ofshafts 2 l, 23 no longer To efiect this, the electrical or otherimpulses from the gyroscope G actuate the servomotor it to cause thetravelling nut l2 thereon to move downwardly sufficiently for the gimbalrings and 5'! to assume the horizontal position shown in Figs. 8 and 9.The servo-motor i5 is not actuated so that the coplanar position of thetwo gimbal rings remains unchanged.

The unitary change in position of the two gimbal rings 62 and 6?, withrespect to the plane of the airplane part Ill, causes the cam followersit? and at through their associated cranks and linkages to effectcompensating motions of the reflector H about its pivot M andsimultaneously a compensating rotation of the shaft l5 in the bearing H,as the shafts 23, 2! continue to be rotated or oscillated. These motionsmaintain the reflector H in the same relative position as shown clearlyin Fig. 2 and in Fig. 8. In other words, the roller 49 moving in thetrackway of the gimbal ring f5? through the cranks Al, 45, linkage M,crank 42, crank ill, cam follower 39, slide rods 3'4, crossbar 33, crossmember 32, cam follower 36 and cam 26 operates to maintain the radiatorI2 along a horizontally disposed axis by tilting the reflector H fromits initial position relative to the pivot l4 sufficiently to compensatefor the angular shift of the longitudinal axis of shaft M, It relativeto the horizontal. At the same time, the cam follower also moving in thegimbal ring groove 61a operates the yolk 51, the

linkages i5, 53 and crank -5I to impart a compensating rotation of-the-stub shaft I5 about its longitudinal axis'soas to maintain thereflector I I in its initially adjusted-position. For example,

if the upright arm 82a of the biasing member 82 that engages thereflector -II is chosen as a reference, it will be observed from Figs.1, 2, 8 and 9 thatit must maintain its vertical upright position. Toeffect this there must be 'compensating angular rotation of the shaftI5, I6 so that the reflector remains in its initially adjusted positionand the transverse axes A-A, BB of the beamradiated from the reflectorII remain unchanged-despite the fact that the transverse axis of theairplane, and the axis of shafts 2 I, 23 have been inclined to an'extentcorresponding to the angle of bank.

When the 'plane undergoes both pitch and bank, the frame part II] andshafts I5, I6, 2I and 23 undergo corresponding angular changes both withrespect to the angle of bank and with respect to'the angle'of pitch. Theframe part I and shaft I5, IS in Figs. 10'and 11 are shown at the doubleangular disposition assumed for a specific bank or roll anda specificpitch. The movements of the gyroscope parts in'the airplane tocompensate for'these changes are transmitted as impulses through lines'L and M to the respective servomotors l0 and I5. The threaded shafts IIand I6 of 'these motors as a result are rotated in required directionsin response to the impulses received from the gyroscope control toeifect movement of the respective travelling nuts I2 and TItocause-compensating movements of the respective gimbal rings 62 and 61to bring them to the relative positions shown in Figs. 10 and. 11.Therein, because of the fact that the plane part II] has undergone botha bank and a pitch the result is that these gimbal rings 62 and 61assume positions that no longer are coplanar but such that the planes ofthese two gimbal rings lie angularly disposed relative to each other.The angular disposition is sufficient for the rollers 49 and 60 movingover the trackway 61a of the inner gimbal ring I57 to impartcompensating movements to the linkages and-cranks connected to thereflector I I and to the stub shaft I to maintain the reflector I Iinits initially adjusted position wherein the longitudinal axis of theradiator I2 remains horizontal and the transverse axes A--A-and 3-43 ofthe beam reflected from the reflector I I remainunchanged.

Theservo-motors Ill and I5 are highly sensitive and substantiallyinstantaneous in their response to thechangingpositions of the gyroscopeparts which in turn shift with the bank and tilt of the plane so thatthe gimbal rings 62 and 61 move substantially instantaneously tocompensating positions as a result of the action of their servo-motorsIII and I5. Consequently compensating angular movement of the reflectorII about the pivot I4 and compensating angular rotation of the stubshaft I5, I6 about its longitudinal axis to maintain the initiallyadjusted .position of the reflector II are effected. Thus,

with the mechanism described herein, the disposition of the radar beamrelative to the target remains unchanged irrespective of bank and pitchof the airplane.

The function of the tiltmotor .29 which is controlled from a cockpit issimply to provide an initial adjustment of the.cam.26 and thereby toprovide an initialposition of the reflector II and its radiator I2relative to the target. For example,

'it may :be the horizontal disposition of the radia- 1 conditions.

.tor I2 shown in-the-figures, or else, by adjustment ofthe cam 26, theradiator I2 may be adjusted to a position such that its longitudinalaxis lies at an angle with the horizontal (not shown). Irrespective,however, of what initial adjustment ismade of .theradiator I2, until thetilt motor 29 is again actuated, the action of the servo-motorcontrolled gimbal rings 62 and 51 will be such as to maintain'theadjusted disposition of the radiator I2 and reflector II until a furtheradjustment is made of the tilt motor as required by changed targetconditions. The angle of pitch or angle of bank of the plane, however,will automaticall be compensated for by compensating shifts of the twogimbal rings 52 and 61 so that roll or pitch of the plane will beimmaterial in so far'as the radar beam which is transmitted to thetarget is concerned.

The'entire mechanism described is, for practical purposes, positioned ina protected region of the plane, for example, in a blister on the planefuselage or in front of a Plexiglass or other transparent opening in theplane so as to be unaffected by atmospheric conditions. Thecomparatively light weight of the parts operating the reflector II andradiator I2 eliminates largely the problem of inertia of large massesand permits the use of simple low powered servo-motors that are verysensitive and quick to respond to changing Also, the light weight of thelinkages and cranks eliminates largely the problem of inertia in so faras movements thereof are concerned in response to positioned changeseffected in them by the changes in positions of the gimbal rings 62 and61.

In effect, the gimbal rings 62 and El are activated upon deviation fromthe normal initial position of the axis of the shaft parts 2|, 23 sothatcompensating angular rotation is given to the shaft I5 through crank5| and associated linkages and the cam follower 60 moving in the groove61a of the gimbal ring 6? and so that compensating tilting motion aboutthe axis I4 is given to therefiector I I through the cranks, linkages,and slide rods coupled to the cam follower 6'9. As a result thereflector is maintained in its initially adjusted position withreference to the target .irrespective of the deviations from normal"gositon during flight of the axis of shaft parts While a specificembodiment of the invention has been shown in the various figures anddescribed herein, it is to be understood that variations in structuraldetail are possible and are contemplated. There is no intention,therefore, of limitation to the exact details shown and described.

What is claimed is:

l. In radar antennae equipment for use with aircraft, a radar beamreflector, a member rotatably supported at a fixed angle relative to asupport axis, means for pivotally supporting said reflector fromsaidmember, an outer gimbal ring, means for pivotally supporting said gimbalring, an inner gimbal ring concentric with the outer gimbal ring, meansfor pivotally supporting said inner gimbal ring from the outer gimbalring, said inner gimbal ring having an annular groove, cam followersmovable on said groove, means coupling one of said followers to saidmember to effect compensating rotation thereof and means coupling asecond'of said followers to said reflector to effect a compensatingpivotal motion thereof .in response to positional changes of said gimbalrings resulting from positional changes of the aircraft in flight tomaintain said reflector in an initially adjusted disposition relative toa target.

2. In combination with a radar reflector adapted for rotation about asupport axis, that has a fixed normal position relative to an aircraft,a rotatable shaft, means for pivotally supporting said reflector fromthe shaft for tilting on an axis perpendicular to the shaft axis, anouter gimbal rin means for pivotally supporting said ring, an innergimbal ring supported pivotally from the outer ring, cam followersmovable over a surface of said inner ring, means for coupling one ofsaid followers to said rotatable shaft, means for coupling another ofthe followers to said reflector, and servo-motor means for effectingcompensating movements of the gimbal rings required by deviations fromthe normal position of the support axis during flight of the aircraftwith corresponding transmission to the reflector of compensatingmovements through the cam followers and coupling means associatedtherewith to maintain said reflector in an initially adjusted positionwith reference to a target.

3. In combination with a radar reflector adapted for rotation about asupport axis that has a fixed normal position relative to an aircraft, arotatable shaft, means for pivotally supporting said reflector from theshaft for tilting on an axis perpendicular to the shaft axis, an outergimbal ring, means for pivotally supporting said ring, an inner gimbalring supported pivotally from the outer ring, cam followers movable overa sur- 10 face of said inner ring, means for coupling one of saidfollowers to said rotatable shaft, means for coupling another of thefollowers to said reflector, servo-motor means for effectingcompensating movements of the gimbal rings required by deviations fromthe normal position of the support axis during flight of the aircraftwith corresponding transmission to the reflector of compensatingmovements through the cam followers and coupling means associatedtherewith to maintain said reflector in an initially adjusted positionwith reference to a target, and means responsive to said deviationsresulting from changing disposition of the longitudinal and transverseaxes of the aircraft during flight for operating said servo-motors.

THEODORE W. KENYON.

REFERENCES CITED The following referenlces are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,047,922 Seligmann July 14, 19362,080,490 Kollsman May 18, 1937 2,170,087 McPherson Aug. 22, 19392,396,038 Bossi Mar. 5, 1946 2,405,058 Ross July 30, 1946 2,407,275Hays, Jr Sept. 10, 1946 2,407,310 Lundy et a1 Sept. 10, 1946 2,412,631Rice Dec. 17, 1946

